An image sensor is a sensor that detects and measures light incident thereon in order to convey the information that constitutes an image. To that end, an image sensor typically comprises a plurality of photodetecting, or photosensitive, elements such, as e.g. photodiodes, configured to convert light incident thereon into electrical charge. An image sensor may be viewed as a grid, or an array, of imaging pixels, each imaging pixel comprising a photodetecting element, typically individually addressable and individually controllable, for measuring light incident thereon.
A charge-coupled device (CCD) is a device for the movement of electrical charge, e.g. from an area where the charge was generated to an area where the charge can be manipulated, e.g. converted into a digital value and possibly followed by further digital processing of the digital value. A CCD may be viewed as moving charge between capacitive bins (potential wells or charge reservoirs) in the device, with the shift allowing for the transfer of charge between bins.
A CCD image sensor is a particular class of image sensors capable of acquiring images, sometimes referred to as “image frames,” in which a CCD is used to store and read out the charge accumulated by the photodetecting elements. As used in the art, “acquisition” of an image frame, referred to, interchangeably, as an “exposure”, or an “acquisition of an exposure” or a “capture” of an image frame/exposure commonly refers to the collection of photo-generated electrons from the light of a target scene by individual photodetection elements or pixels for a specific period of time (“exposure time” or “period” or “acquisition time” or “period”). As also used in the art, “read-out” of an image frame or an exposure commonly refers to the transport of the collected charge from the storage elements to additional circuits which convert the charge to voltage or current for subsequent digitization of the pixel information.
CCD image sensors are often incorporated into image acquisition systems employed in various settings. Performance of such image acquisition systems is influenced by the image acquisition and read-out capabilities and characteristics of the CCD sensors included therein. Further improvements with respect to acquisition and read-out of image frames in CCD image sensors are always desirable.